Manufacturers of high quality fabric articles, such as napkins, generally "finish" the corners of the article in some fashion. The threads in the corners have a tendency to unravel and present a nonuniform appearance unless the threads are sewn or fused together. Sewing the corners, however, is expensive and time consuming given the attention to detail that is required to produce a uniformly sewn article.
Attempts have been made in the past to seal the threads of a synthetic or blended fabric material article by applying heat to the article. For example, one known method uses a heated blade that seals the edges of the article as it cuts the fabric. The melted fabric material, however, tends to build up on and near the cutting blade. This buildup of material requires constant inspection and cleaning. The system therefore has limited efficiency because of the required down time. The excess melted material also tends to spoil the appearance of the finished product. Further, the heat generated from the cutting blade affects the efficiency and lifetime of the other mechanical items of the system in the immediate area of the blade. The heat also may present a safety hazard to the operator.
Another known system seals the fabric threads at the corner of an article by placing the fabric article between a hot wire and a porcelain plate. The hot wire cuts and seals the fabric. As with the first system, however, this method has significant maintenance and quality problems. The melted material also tends to build up on the plate or the wire. Further, the wire tends to break frequently because of the heat and force involved in the cutting action.
Other known methods have used a flame or heated air to seal the edges of multiple layers of plastic fabrics piled in a stack. For example, U.S. Pat. No. 2,849,347 to Uziel describes subjecting a stack of staggered layers of plastic material to flame or hot air to seal the edges of the material and to prevent fraying. The drawbacks to this method include the fact that the layers have a tendency to stick together, even if staggered. The method also inevitably fails to finish several layers due to uneven stacking. Further, this method is not adaptable to high quality fabric articles because heating the entire edge of an article tends to distort the straightness of the edge, and thus the uniform appearance of the article.
What is needed therefore is a means for sealing the corners of a fabric article in an efficient, automated process. Known system either require to much maintenance and attention or do not produce a sufficiently uniform and high quality product.